CLADOENDESIS OF EPHEMEROPTERA
Nomen hierarchicum: Acanthametropus/fg1 [f:1963; g:1948] (incl. Analetris)
In circumscription fits:
subfam. Acanthametropodinae: Hubbard 1982: 50
fam. Acanthametropodidae: McCafferty & Wang 1994b: 214
Acanthametropus/fg1: Kluge 2004: 88
References. Edmunds & Koss 1972: *; Edmunds & Jensen & Berner 1976: * *; Kluge & Studemann & Landolt & Gonser 1995: * *; Kluge 2004: * * *.
Autapomorphies of Acanthametropus/fg1.
(1) Mouth apparatus is specialized for carnivorism, both Analetris and Acanthametropus/fg2 pray on chironomid larvae. Labrum with wide median incision. Asymmetry of mandibles is lost; each mandible is shortened perpendicular to axis of articulation and elongated along this axis, incisor and kinetodontium are stout, prostheca is lost, mola lacks grater. Superlinguae are vestigial (Kluge & al.1995: Fig.23-30). Maxillae are stout, biting; apical setae are absent; canines and dentisetae are situated in one plane, only two canines are present, first and second dentisetae are canine-like, third dentiseta can be vestigial or lost (Kluge 2004: Fig.23:B) [see Plesiomorphies of Tridentiseta]. 2nd (penultimate) segment of labial palp is widened (Kluge 2004: Fig.23:C).
(2) Larval legs are specialized [see (3) and (6)], fore and middle legs differ from hind ones: femora of fore and hind legs are widened, claw of hind leg is much longer than claws of fore and middle legs (Tshernova 1948: Fig.3).
(3) On each leg tibia is shortened, tarsus is elongate; on imaginal and subimaginal middle and hind legs 1st tarsal segment is longer than tibia.
(4) Sterna with median projections: in larva projection is present at least on prosternum and mesosternum, in imago on prosternum (Kluge 2004: Fig.23:D-E) (in larval Acanthametropus/fg2 projections are present not only on thorax, but on abdomen also).
(5) Each tergalius IVII consists of 3 lamellae: dorsal lamella is initial one, and 2 ventral lamellae represent 2 parts of expanded anal-proximal lobe bent down. In Analetris each of these 3 lobes has integral margins (Edmunds & Koss 1972: Fig.4), while in Acanthametropus/fg2 these lobes are strongly dissected and their projections are tangled (Kluge 2004: Fig.23:A). Anal rib is lost, thus only costal rib is present on initial (dorsal) lamella.
(6) Entire larval body is dorsoventrally flattened and widened, claws are strongly elongate [see (2)] (Tshernova 1948: Fig.1-3; Burks 1953: Fig.312; Edmunds & Koss 1972: Fig.1). Non-unique apomorphy the same in some other specialized psammophils, such as Ametropus and Pseudiron.
(7) Larval abdominal terga and sterna bear stout scales i.e. flattened setae (whose sockets are not widened, unlike scales of Turbanoculata) and lack denticles on posterior margin (Lehmkuhl 1976: Fig.13). Non-unique character.
Plesiomorphies of Acanthametropus/fg1. Larva retains features of primary swimming siphlonuroid specialization: legs are able to stretch posteriorly [in spite of specialization see (2), (3), (6)]; abdomen is large, able to make undulate swimming movements; caudalii are not long, paracercus is well-developed, primary swimming setae are dense, secondary swimming setae are absent. Larval head is hypognathous. Labial palp [see (1)] is 3-segmented. Larval (and adult) patella-tibial suture [on short tibia see (3)] is developed on middle and hind legs only. Larval claws [see (2)] are slightly curved, without denticles.
In imago and subimago: Mesonotal suture is nearly transverse (at least in Acanthametropus/fg2). Anterior paracoxal suture is complete (Kluge 2004: Fig.23:E) (unlike Rallidens and some Bidentiseta). Furcasternal protuberances are contiguous (Kluge 2004: Fig.23:E) (unlike Amphinotic groups of Tridentiseta and some others see Index of characters [2.2.23]). Subimaginal lateral pigmented area of mesonotum is small, stretches along lateroparapsidal suture and does not occupy sublateroscutum (Kluge 2004: Fig.23:F) (see Index of characters [2.2.14]). In cubital field of fore wing several (38) veins go from CuA to basitornal margin or anastomose and can be partly substituted by intercalaries [see Anteritorna (1)]; hind wing is well-developed, as long as 0.450.5 of fore wing length (Kluge 2004: Fig.24:A-B). Imaginal and subimaginal tarsi are 5-segmented, 1st segment [long see (3)] is fused with tibia. Claws are ephemeropteroid [exception can be made by male fore legs only see below, Acanthametropus/fg2 (6)]. Imaginal and subimaginal paracercus is subequal to cerci.
Size. Fore wing length 1220 mm.
Age and distribution. Recently distributed in Amphipacific Sector of Holarctic: Eastern Palaearctic and Nearctic. Reporthed from Baltic amber (see Analetris).
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